This invention relates generally to projection television receivers and is particularly directed to an integrated multi-cathode ray tube (CRT) and lens mount for a projection television receiver.
In a projection television system, an image generated on the face plate of a CRT is magnified through a lens and projected onto a screen. In a color projection television system, there are three CRT's which separately display red, green, and blue images which are projected onto the screen in an overlayed arrangement. These three CRT's are typically arranged in a triad, or side-by-side, along a horizontal axis. In a multi-CRT color projection television, the images of each of the three CRT's must be precisely superimposed so that a single image appears upon the projection screen. Each image must be exactly the same size and shape to effect precise superposition. A center CRT is typically projected perpendicular to a screen or to a mirror which reflects the image onto the projection screen, while two outer CRT's are projected at respective angles relative to the optical axis of the center CRT such that superposition is achieved.
In some projection television systems, CRT alignment is provided by electronic image alignment circuitry which electronically compensates for projected image geometric distortions. However, adjustment of this electronic alignment circuitry is generally time-consuming and requires a high level of skill by the manufacturing assembler or one who repairs the projection television. Mechanical arrangements have also been proposed for the positioning and alignment of multiple CRT's in a projection television system. These mechanical mounting arrangements have typically involved a plurality of interconnected structural components which require tightening and adjustment for proper positioning of the CRT's in a mounting frame. The positioning of one CRT in the mounting frame generally affects the alignment of the other CRT's frequently resulting in image misregistration. With several different mounting components requiring adjustment to varying degrees, precise alignment of the three CRT optical axes becomes very difficult, if not impossible.
U.S. Pat. No. 4,404,588 to Fanizza et al discloses a CRT holding assembly for a projection television which employs three pods, each supporting a respective CRT. Each of the pods is, in turn, mounted by means of plurality of bolts to a platform. Each platform includes a cylindrical housing for holding the front piece of a CRT and a back cover which holds the CRT inside the housing. This arrangement therefore requires precise relative positioning of each of the CRT's within a respective housing as well as precise positioning of each housing upon the platform. U.S. Pat. No. 4,400,723 to Fanizza et al discloses a stationary optical assembly for a multi-CRT projection television including a CRT holding assembly, a mirror and a chassis mounting arrangement. The CRT holding assembly includes three pods mounted on an integral, respective base plate, with the base plates mounted, in turn, upon a bed plate. The chassis includes a plurality of threaded studs for mating with respective apertures in the pod-mounting base plates. While providing for the simplified and precise positioning of the CRT mounting assembly within the chassis, the CRT mounting assembly includes a plurality of individual components which must be fitted together and securely attached to a respective CRT as well as to a base or CRT holding assembly. The large number of connections required increases the likelihood of optical misregistration between the various CRT's.
U.S. Pat. No. 4,506,295 to Young et al discloses a unitary optics frame for a projection television receiver comprised of a plurality of tubular members interconnected to form a rigid skeletal structure. The skeletal structure incorporates various sub-frames to which the projection tubes, mirror assemblies and screen are mounted for maintaining the various positional relationships therebetween. While providing a unitary support structure for these projection television components, the orientation of these components in the support frame requires precise adjustment for proper alignment.
The present invention is intended to overcome the aforementioned limitations of the prior art by providing an integrated lens and CRT mount for a projection television receiver which affords precise positioning and alignment of the various CRT's and lenses therein without requiring a complicated position adjustment procedure. The integrated lens and CRT mount includes a unitary structure which is inexpensive, involves a minimum number of components, and facilitates the installation and alignment of the aforementioned projection television components without a complicated installation procedure or individual adjustment of the CRT's and lenses.